1. Field of the Invention
The present invention relates to a compressor including, in a housing, a compression mechanism for sucking, compressing and discharging refrigerant and a reservoir for storing liquid for lubricating sliding portions including the compression mechanism.
2. Description of the Related Art
This type of compressor is made air-tight by connecting the housing to a refrigeration cycle. When the compression mechanism is driven, the compression mechanism sucks refrigerant in the refrigeration cycle via a suction port of the housing, and then compresses and discharges the refrigerant into the housing so as to supply the refrigerant to the refrigeration cycle via a discharge port of the housing. The above process is repeated. In conjunction with the above process, lubricating oil stored in the reservoir of the housing is supplied to the sliding portions including the compression mechanism directly or via transfer by the refrigerant, thereby lubricating the sliding portions. This allows maintenance-free operation of the compressor. The refrigerant discharged by the compression mechanism to be supplied to the refrigeration cycle contains the lubricating oil. The lubricating oil contained in the refrigerant may deteriorate the performance of the refrigeration cycle. In addition, in a case where much lubricating oil circulates in the refrigeration cycle at the same time, the lubricating oil in the sliding portions in the housing goes short. In this case, in order to make up for this short of lubricating oil, it is necessary to increase the capacity of the reservoir and the amount of lubricating oil that can be supplied, thus increasing the size and weight of the compressor.
In order to overcome the above problem, techniques have been conventionally known in which the lubricating oil in the refrigerant discharged from the compression mechanism is separated from the refrigerant by centrifugation before the refrigerant is supplied to the refrigeration cycle and the separated lubricating oil is returned to the reservoir in the housing. See Japanese Patent Laid-Open Publication Nos. Hei 07-151083 and Hei 11-082352, for example. According to this technique, the refrigerant discharged from the compression mechanism and the lubricating oil are separated from each other by centrifugation in accordance with a so called cyclone system. More specifically, the refrigerant discharged from the compression mechanism is tangentially introduced into an upper portion of a cylindrical centrifugal chamber that is arranged perpendicularly to the axial line of the compressor, so as to form a spiral downward flow in the introduced refrigerant, which travels downward along the cylindrical surface of the centrifugal chamber, thereby separating the lubricating oil from the refrigerant. The refrigerant thus separated is then made to flow from the lower portion of the centrifugal chamber, pass through the central portion thereof, and go out of the centrifugal chamber upward to enter the refrigeration cycle. The lubricating oil thus separated is caused to blast out from the lower portion of the centrifugal chamber into the housing of the compressor so as to be returned to the reservoir.
According to the method disclosed in Japanese Patent Laid-Open Publication No. Hei 11-082352, the lubricating oil after separation by centrifugation is blasted out in a parallel direction to a surface of the lubricating oil stored in the reservoir so as not to fluctuate the lubricating oil surface. In this manner, the level of the lubricating oil stored in the reservoir is kept constant and the supply of lubricating oil to the sliding portions is stabilized. Also, a back-flow of the lubricating oil in the reservoir to the centrifugal chamber caused by the fluctuation of the lubricating oil surface can be prevented.
In recent years, a sealed type compressor mentioned above has been installed in a vehicle for air-conditioning of a vehicle compartment. The vehicle is required to reduce its weight because of growing interest in environmental and energy problems. Especially, the weight reduction in the vehicle is the most significant issue since in an electric vehicle or hybrid vehicle the same level of driving force as that of a gasoline-powered vehicle cannot be obtained. Thus, it is significant to reduce the size and weight of the compressor that is relatively heavy, in particular, an electric compressor that further includes an electric motor in a case where the compressor is mounted on a vehicle.
However, the aforementioned cyclone type separation mechanism for separating lubricating oil, that is used in the above conventional compressor, necessitates a larger space that ensures formation of both a flow of refrigerant that is being separated by centrifugation, which goes downward in the centrifugal chamber while being pressed against the cylindrical surface of the centrifugal chamber to leave lubricating oil on the cylindrical surface and another flow of refrigerant after separation that goes from the lower portion of the centrifugal chamber, passes through the central portion and then goes out of the centrifugal chamber upward to be discharged from the centrifugal chamber. The separation mechanism becomes relatively large in a diameter even if a cylindrical wall for separating those flows from each other is provided. Thus, the size of the space occupied by the separation mechanism in the housing of the compressor becomes larger in the direction of the axial line of the compressor, preventing the size and weight reduction.